The copyright and license notice is already in the LICENSE file. There
is no justifiable reason to also require that it be included in every
file, since the individual files are not individually distributed except
as part of the entire package.
This is mostly working, but not completely ideal for two reasons.
1. Rather than emitting an error on the ChildProcess object when the
setgid/setuid fails, it is simply printing the error to stderr and
exiting. The same happens with the cwd, so that's not completely
terrible.
2. I don't have a good test for this. It fails with an EPERM if you try
to change the uid or gid as a non-root user.